I have one suggestion: Maybe a little to late in the development, but it really bothers me :

When I bet my first Vicious Dungeon, I was really excited to find a vicious trophy that I can prep. You get one, but only INSTEAD of a locker item. With most of them being not THAT extrastrong, it felt kind of disappointing. I would love an extra building where all your vicious trophies are, that can be prepped aswell. Maybe make them twosided, so the balance doesnt get to wasted. But something that helps you defeat another vicious, because you beat the first one. This would be an awesome motivation in the lategame

I can say with 100% confidence that we aren't ever going to have two locker-like prep lines at the same time. However, people have proposed that the VICIOUS artifacts be given their own unique locker slots that do not replace the existing ones. I've always liked this idea. Besides the convenience factor, it helps mark them as special and unique.

I think you underate the artifacts. Only the Symbol is weak. The Shield and the Ward are in WTFOMG territory, reigned in only by their totally impractical preparation price.

The shield and the ward are ridiculous-by-design and warp gameplay just by being available as preps. They don't look like much at first sight, but boy are they broken once you pick up on the unwritten "availability of options" list.